Prevention and treatment of "new three diseases" of grass carp

With the increase of culture density and the deterioration of culture environment, grass carp culture diseases developed from traditional "old three diseases" (red skin, rotten Gill, enteritis, etc.) to "new three diseases" of grass carp, namely bacterial complications (red skin, rotten Gill, enteritis complications), viral hemorrhagic disease, hepatobiliary syndrome and so on. The "new three diseases" of grass carp bring greater harm to culture and production, resulting in a large number of deaths of grass carp.

Bacterial complications (red skin, rotten Gill, enteritis)

[etiological symptoms] the pathogens of the disease are caused by a variety of bacteria, including intestinal Aeromonas punctata, Myxococcus fishi, Pseudomonas fluorescens and so on. Fish with this disease have three symptoms: red skin, rotten gills and enteritis.

The diseased fish have black body color, black head, and wander alone; slow response, abdominal enlargement, erythema on both sides, obvious "fin decay", protruding redness and swelling of the anus, purplish red, light pressure on the abdomen, yellow mucus and blood pus. Open the abdomen, you can see peritoneal effusion, intestinal wall congestion and inflammation, especially the hindgut, intestinal mucosal cells often fester and fall off, and mixed with blood to form blood stains, filling in the intestines; the liver often has red spots and congestion. Gill filaments of diseased fish are punctate hyperemia, end decay, cartilage exposure, resulting in whitening of the edges, mucus and silt on the Gill filaments, hyperemia, inflammation and decay of the operculum epidermis in severe cases, and the middle part is often burned into a round transparent window, commonly known as "open skylight"; local inflammation on the body surface, scales loose and falling off, obvious on both sides of the abdomen, fin base hyperemia, end decay, scale exfoliation or fin decay often have water mold parasitism. The disease can occur in a year, especially from May to September.

[prevention and control methods] thoroughly clean and disinfect the ponds, carry out "Sixiao" and "Siding", do not directly use unfermented animal feces, do not feed rotten and deteriorated feed, and soak fish fry with 3% salt water before stocking.

[treatment method] disinfectants such as 0.2ppm chlorine dioxide or 0.3ppm bromochlorohydantoin or 0.4ppm strong chlorine were sprinkled regularly in the whole pool, garlicin 100g for every 40 kg feed for 7 days and enrofloxacin 100 g for 3 days for 3 days.

Hepatobiliary syndrome

[etiological symptoms] Grass carp hepatobiliary syndrome is a common disease in grass carp culture. at the initial stage, diseased fish in the pond drift to the edge of the pond, slow response, reduced food intake, visual body surface no obvious symptoms, only a small number of fish eyeballs and eye sockets are red, Gill filaments are swollen, and there are no parasites in microscopic examination. Anatomy found that there was no food in the intestine, and the liver was swollen, white, green or yellow, which were all symptoms of hepatobiliary syndrome. The severe liver was scattered and adhered to intestinal mucosa and fat, filled in the chest, and the gallbladder sometimes swelled and blackened. Sometimes the gallbladder became absent and the ascites was severe. After a period of time, the number of dead fish increased sharply; the cause of the disease is more complex, feeding metamorphic feed, excessive fat content in feed or long-term feeding of quinolinol feed, fish culture water polluted by copper, ammonia and other substances will cause liver disease.

[prevention and control methods] pay attention to reasonable stocking density, do not feed spoiled feed, do not directly apply unfermented animal feces, often inject new water or use biological agents to improve water quality, often remove feed residues and establish an inspection system for fish feed, keep the feed fresh and prevent the oxidation of protein and fat in the feed.

[treatment method] disinfectants such as 0.2ppm chlorine dioxide or 0.3ppm bromochlorohydantoin or 0.4ppm strong chlorine were sprinkled in the whole pool regularly, and the bait was made by feeding 40kg with 100g of Gandanning and 100g of allicin for 5 days.

Viral hemorrhagic disease

[etiological symptoms] in the early stage of the disease, the oral cavity, abdomen, operculum, orbit, fin and both sides of the fish showed mild hyperemia. When the abdominal cavity was opened, a small amount of food was still found in the intestines. With the development of the disease, the above body surface congestion intensified, flesh and bone showed bleeding symptoms, orbital congestion, exophthalmos, abdominal swelling, redness and swelling. Open abdominal cavity, due to damage to internal organs, resulting in the accumulation of yellow or red ascites, liver, spleen, kidney swelling, intestinal wall congestion, inflation and no food. Gill gray shows anemia, sometimes purple and swollen, and in severe cases, the ends of the Gill filaments rot.

[Epidemiology] from March to April, the symptoms of inflammation and congestion on the body surface of diseased fish were as follows: head, mouth, operculum, orbit, both sides of body surface, ventral fin and caudal stalk, etc. exophthalmos and Gill anemia can be seen in some diseased fish. internal organs are accompanied by varying degrees of inflammation, and sometimes inflated and inflated intestines can be seen. The symptom of diseased fish after 5 months is that the body surface is inflamed by congestion of the lower margin of the operculum, fin base and internal organs, and sometimes the flesh and bones of the mouth are also congested and inflamed at the same time. The disease is widely prevalent in grass carp culture, and the water temperature may occur between 9 and 36 ℃, especially at 28 ℃, which often causes great economic losses. therefore, it is an epidemic with the widest epidemic area, the longest season and the greatest harm.

[prevention and control methods] thoroughly clear the pond and disinfect the pond, carry out "Sixiao" and "Siding", and often inject new water or use biological agents to improve water quality.

Treatment: regularly sprinkle the whole pool with disinfectants such as 0.2ppm chlorine dioxide or 0.3ppm bromochlorohydantoin or 0.4ppm strong chlorine; take 10% enrofloxacin 100g + Sanhuang powder 200g and feed 40kg for 5 days.